Plasma-generating electrode device, an electrode-embedded article, and a method of manufacturing thereof

ABSTRACT

A plasma generating electrode device including a substrate 31 made of a dense ceramic, and an electrode 55 buried in said substrate 31, wherein said electrode 55 is isolated from a setting face of said substrate 31, and plasma is generated over said substrate. It is preferable that the minimum thickness of an electromagnetic wave permeation layer 37 is not less than 0.1 mm, the average thickness of the electromagnetic wave permeation layer is not less than 0.5 mm, the electrode 55 is a planar electrode made of a metal bulk, and the electrode is a monolithic sinter free from a joint face. This structure can be applied to an electric dust collector, an electromagnetic shield device or an electrostatic chuck. These can be preferably installed inside a semiconductor production unit using a halogen-based corrosive gas. The electrode can be embedded in the dense substrate made of the joint face-free monolithic sinter by hot press sintering a ceramic molding and the electrode made of the planar metal bulk under pressure applied in a thickness direction of the electrode.

TECHNICAL FIELD

The present invention relates to an electrode-embedded article such as aplasma-generating electrode device usable for semiconductors, or thelike, a method of manufacturing such an electrode-embedded article, andan electromagnetic wave permeation body to be preferably used in suchelectrode-embedded articles.

BACKGROUND OF THE INVENTION

For semiconductor device production units requiring super-cleanconditions, corrosive gases such as chlorine based gas, fluorine basedgas and the like are used as a depositing gas, an etching gas, and acleaning gas. Therefore, if a conventional heater wherein the surface ofa resistance heating element is covered with a metal, such as stainlesssteel or Inconel, is used as a heater to heat wafers which are exposedto the corrosive gas, unfavorable minute chloride, oxide, fluoride, andother particles with diameters of a few μm are formed due to theexposure of that metal to the corrosive gas.

In view of this, with those etchers and CVD units running at lowtemperatures, as illustrated in FIG. 1, by way of example, anarrangement used to be adopted, wherein infrared lamps 5 are installedoutside a chamber 1 via a quartz window 4, the chamber interior beingexposed to deposition-gas, etc.; a susceptor 2 made of aluminum forexample is installed within the chamber 1 through an arm 3; and thesusceptor 2 is heated by the infrared lamps 5, whereby a wafer W placedon the susceptor 2 is indirectly heated. In this arrangement, the metalsusceptor 2 is used as an electrode for plasma generation, plasma isgenerated within the chamber 1 with high-frequency electric energy feddirectly to susceptor 2 so as to form a semi-conductor film on the waferW and clean it. In this case, the aluminum susceptor 2 has an insulatingfilm of alumina with a thickness of approximately 10 μm formed over itssurface through an anodized aluminum production process so that wafer Wwas placed on this insulating film might be prevented from againstdirectly receiving high-frequency electric energy. High-frequencyelectric energy discharging takes place with this insulating filmmaintained charged at a certain level within the plasma, since nocharges flow to either one electrode, unlike current discharging.

However, in the above-mentioned conventional case the susceptor 2 wasmade of a metal, and therefore wafers were unfavorably contaminated withheavy metal. Particularly, the aluminum susceptor 2 was confronted witha problem of Mg-contamination. To solve the problem of suchcontamination, it has been proposed that susceptor 2 be insulating and aplate-like electrode 6 be attached to the rear face of the susceptor forplasma generation, as illustrated in FIG. 2 by way of example.Regrettably however, a further problem occurred wherein the plate-likeelectrode 6 for high-frequency electric energy supply interceptedinfrared rays from infrared lamps 5, and the heating capacity of thesusceptor 2 further declined. In addition, with said susceptor, thepoint of plasma generation deviated from the set position of the waferW, whereby preferable plasma generation was generated, resulting indecreasing wafer cleanability. The susceptor with a ring-like electrodefitted around the outer periphery thereof also caused a similar problem.

Although said insulating film remains charged at a certain level in thestage of plasma generation for such processes as physical vapordeposition (PVD process), chemical vapor deposition (CVD process) or inan etching unit, electrolytically dissociated ions and electrons collideagainst the charged insulating film to damage said insulating film.Particularly, the anodized aluminum insulating film lacking densenessand having a thickness of approximately 10 μm at most gave a shortservice life. Especially with the CVD process unit, an etching unit andthe like using halogen-based corrosive gas, the anodized aluminuminsulating film having such short service life requires frequentreplacement. It was discovered that particularly the metals such asaluminum, etc. had undergone heavy corrosion by the plasma of thehalogen-based corrosive gas, whereby the susceptors of these metals wentthrough serious deformation to such an extent that the susceptors failedto provide normal service.

The inventors discovered the following problem referred to hereunder inthe course of investigations. Namely, in such a process using plasma asreferred to above, the molecules of the gas are first dissociated torelease highly reactive positive ions and electrons and thereby generatea plasma zone. Since the electrons which electrolytically dissociated atthat time each have a smaller mass, they move more rapidly as comparedwith ions, resulting in producing a region with a smaller electrondensity near a high-frequency electrode. This region with the smallerelectron density is called a plasma sheath. Utilizing the potential ofthe plasma sheath, the ions within the plasma are accelerated, and theaccelerated ions are brought into collision against the wafer surface.Ions of different species are selectively applied respectively foretching, CVD and PVD.

But, in the case with the susceptor of anodized aluminum applied asreferred to above, the plasma sheath did not grow stably, sometimesfailing to assure stabilized plasma discharge. As a consequence, theresometimes occurred failure of effecting stabilized etching, CVD and PVDover the entire surface areas of the susceptor.

In the semiconductor device production units, an electrostatic chuck isnow used for the purpose of the transfer, the exposure to light, filmformation, micro-processing, cleaning, dicing, and so on for the wafers.The following are known as an electrostatic chuck:

(1) An electrostatic chuck which is obtained through screen-printing afilmy electrode on a disk-like ceramic green sheet, placing anotherdisk-like ceramic green sheet on the resultant to cover thescreen-printed filmy electrode, followed by press-molding, and sinteringthe resulting ceramic green sheet assembly. Pressing the ceramic greensheet molding inevitably causes non-uniform pressurization, whereby thethickness of a dielectric layer of the electrostatic chuck becomesnon-uniform, thus resulting in not only rendering difficult themanufacture of such chucks, but also reducing the yield of productionthereof.

(2) To solve this problem, the present inventors developed electrostaticchuck 7, schematically illustrated in FIG. 3. That is, a disk-likedielectric plate 8 of dense and insulating ceramic and a disk-likesupport 10 of insulating ceramic are prepared. The disk-like support 10has a through hole 11. Further, a circular sheet of a conductive bondingagent and a columnar terminal 12 are prepared. The circular sheet isheld between the disk-like support 10 and the back side of thedielectric plate 8. The columnar terminal 12 is put into through hole11. In this state, the resulting assembly is thermally treated andthereafter, the dielectric plate 8 and the disk-like support 10 arebonded together, using the conductive bonding agent layer 9. Then, thedielectric plate 8 is polished to flatten a wafer-attracting surface 13.

It is however noted that in the process of (1), the thickness of thedielectric layer is likely to become irregular due to certainrestrictions in the production. In this regard, a complementarydescription is made hereunder. In the method in which the respectivegreen sheets are laminated one upon another after providing the printelectrode on one of the green sheets, press-molded and fired, thereinevitably is non-uniform thickness of the dielectric layer and pooradhesion of the assembly components at the respective stages of thepress-molding and the firing. Namely, these problems coincide with thedisplacement of the print electrode inside the sintered assembly. Inview of this, it is difficult to make uniform the thickness of thedielectric layer no matter how fine the surface of the dielectric layeris planed after the monolithical sintering. In the sintering processunder normal pressure, as the assembly size goes up, it is difficult tosecure the denseness of the dielectric layer at 100%, and from thestandpoint of preventing dielectric breakdown, this sintering processdeteriorates its reliability. Moreover, since the electrode is formed bythe screen printing process, the electric resistance thereof isrelatively large. Accordingly, it is difficult to increase the risespeed for actuating the electrostatic chuck.

Meanwhile, in the process of (2), the disk-like support 10 and thedielectric plate 8 are molded, sintered, and mechanicallysurface-polished. Particularly with the dielectric plate, it isnecessary to plane it to make uniform the thickness. Further, it isrequired to bond together the disk-like support and the dielectric platethrough heating with the circular sheet of silver solder or the likesandwiched therebetween. Therefore, it is necessary to implement thegrinding of the disk-like support 10 and the dielectric plate 8, thethickness adjustment thereof, and very troublesome silver-soldering tojoin together said support 10 and said dielectric plate 8, thusresulting in increasing the number of processing steps, and therebyinterfering with efficient mass production. Joining together thedisk-like support 10 and the dielectric plate 8 using a conductivebonding agent such as silver solder or the like leaves behind a jointface along the conductive bonding agent layer 9. However, this jointface gives rise to a factor for the dielectric breakdown under highvacuum condition. Further, with regard to these electrostatic chucks,high-frequency wave generating electrodes, etc., it has been clarifiedthat the following problem occurred. Namely, with semiconductor deviceproduction units, such a method is generally put into practice, whichcomprises the steps of supplying a gas into the unit and applyinghigh-frequency electric power to the gas for the plasma generation.Therefore, said high-frequency wave generating electrodes, and ECR unitsare finding wide use with the semiconductor device production units fordry etching, chemical vapor-phase growth process, and the like.

Where the ECR unit is employed, the electric power in the form of thehigh-frequency waves in the microwave band is applied to the gas,whereby ECR locally generates plasma within the high-frequency electricfield and also within the static magnetic field with a spatiallyirregular intensity distribution. Subsequently, a force is applied tothe plasma in a certain direction to accelerate the plasma. In the ECRunit, a 2.45 GHz is generally employed as the microwaves. The microwavesare radiated, through an electromagnetic wave permeation window, intothe ERC unit, so that plasma is generated in the gas molecules.

As this electromagnetic wave permeation window is exposed to themicrowaves having high energy, it is essential for this window to atleast release heat due to its heat loss. It is also necessary for thewindow to have excellent thermal shock resistance so that the window maybe difficult to be cracked if it is heated. To meet these requirements,the electromagnetic wave permeation window used to be fabricated ofsilica glass in the past.

However, the electromagnetic wave permeation windows of silica glasshave to date incurred damage by ECR plasma, loss in electromagnetic wavepermeability, and breakage. These problems stemmed from the damages ofsaid windows by the plasma.

The inventors attempted to fabricate the electromagnetic wave permeationwindow of alumina or sapphire, and found that these materials sufferedgreater dielectric loss compared with quartz, and that the transmissionof a microwaves through the alumina or sapphire window entailed a localrise in temperature exceeding 200° C. Generally, it is observed thatexposing the electromagnetic wave permeation window to microwaves givesrise to the generation of heat therein due to the inner friction ofmolecules or polar groups within the dielectric material. Quantity Q ofthe heat generated is expressed by Q=kfE² .di-elect cons. tan δ. In thisexpression, k is a constant, f a frequency, E an electric field, and.di-elect cons. a dielectric constant. It was further clarified that asthe alumina or sapphire electromagnetic wave permeation window locallyunderwent intensive heating, such windows of a large diameter over 100mm failed to resist the thermal impact, and were broken.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a plasma generatingelectrode device which can stably generate plasma near a wafer.

It is another object of the present invention to provide a plasmagenerating electrode device with sufficient corrosion resistance againstgenerated plasma.

A further object of the present invention is to stably generate a plasmasheath to stabilize plasma discharge so that processings such asetching, CVD, PVD, or the like may be effected stably over the entiresurface area of a susceptor.

A still further object of the present invention is not only to improvethe reliability of an electrode-embedded article such as a plasmagenerating electrode device, or the like with a view to preventingdielectric breakdown and short circuiting, but also to decrease theresistance of the electrode.

A still further object of the present invention is to provide aproducing process which lessens the number of steps in producing anelectrode-embedded article such as the plasma generating electrodedevice, or the like and in particular the complicated step ofsilver-soldering, or the like being eliminated, whereby the process issuitable for mass production.

A still further object of the present invention is to provide anelectromagnetic wave permeation body for use with the plasma generatingelectrode device, which electromagnetic wave permeation body isresistant to not only damage even upon exposure to plasma but alsobreakdown even when the temperature rises with an electromagnetic wavepassing through the transmission body.

The plasma generating electrode device according to the presentinvention is characterized in that said device comprises a plasmagenerating electrode embedded in a dense ceramic substrate, and saidplasma generating electrode has an insulating property against thewafer-setting surface of the substrate.

The plasma generating electrode device according to the presentinvention is characterized in that said device comprises a dense ceramicsubstrate and an electrode embedded therein; said device is so designedas to generate plasma over the substrate and the thickness of anelectromagnetic wave permeation layer lying between the electrode andthe substrate surface over which plasma is generated is not less than0.1 mm at the minimum.

An opposite electrode is arranged approximately parallel to theelectrode in the substrate of the plasma generating electrode device ofthe present invention, whereby high-frequency electric power can besupplied therebetween. In this case, it may be that high-frequencyelectric power is supplied to the electrode in the substrate with theopposite electrode grounded and vice versa.

The electrode-embedded article according to the present invention ischaracterized in that said electrode unit comprises a dense ceramicsubstrate and an electrode of a planar metal bulk embedded in thesubstrate, and the substrate enclosing the electrode is a jointface-free monolithic sinter.

The method of manufacturing the electrode-embedded article according tothe present invention is characterized in that a ceramic molding and anelectrode comprising a planar metal bulk are hot press-sintered withpressure being applied in a thickness direction of the electrode,whereby the electrode is embedded in a joint face-free monolithic densesubstrate sinter.

Further, the present invention relates to an electromagnetic wavepermeation body for use with the plasma generating electrode device togenerate plasma with high-frequency electric power applied to the gas,wherein at least that surface of said electromagnetic wave permeationbody contacting the atmosphere of plasma being generated, is comprisedof aluminum nitride of which dielectric loss tan δ=10⁻² at 25° C. andwhose thermal shock resistance ΔTc is not less than 300° C. Since theplasma generating electrode device according to the present inventionhas a plasma generating electrode embedded in the dense ceramicsubstrate, a wafer, or the like can be set directly on the substratewith no fear of contamination, and the point where plasma is generatedis near the wafer, whereby both plasma generating conditions and plasmacleaning performance can be improved.

The inventors made further studies in this regard. Namely, as in theforegoing, the inventors have examined the reason why a plasma sheathwas not stably produced over the surface of the anodized aluminumelectrode. According to present theory, it must be that if the surfaceof the electrode is covered with an insulating material, and the surfaceof the insulating material gets a negative potential, the plasma sheathregion grows and the plasma sheath gets stabilized. However, it wasclarified that where thin film was an anodized aluminum as referred toabove, the electrode failed to keep its surface at a negative potentialof a sufficiently large magnitude and uniformity when heated to a hightemperature, so that a uniform and sufficiently stabilized plasma sheathcould not be produced.

Meanwhile, it was thought in the past that increasing the thickness ofthe insulating film would accordingly expand the distance between theplasma region and the electrode, make insufficient the acceleration ofions within the plasma atmosphere, and impart the stability of plasmadischarge.

But, when the electrode was embedded in a dense ceramic substrate andthe minimum thickness of the electromagnetic wave permeation layer wasincreased to not less than 0.1 mm, the plasma sheath region expanded andthe plasma generated was uniformly and stably produced. It was alsofound that even when the thickness of the electromagnetic wavepermeation layer was increased, the dielectric factor of theelectromagnetic wave permeation layer was large by a few to severaltimes as much as that of a vacuum, since that layer comprised ceramic.As a consequence, it was confirmed that there was no fall in theintensity of the electric field between the electrode, and those ionswithin the plasma could be accelerated sufficiently in the plasmasheath, resulting in stabilizing plasma discharge.

According to the present invention, the electrode is embedded in thedense ceramic substrate, and the minimum thickness of theelectromagnetic wave permeation layer lying between the electrode andthe surface of the substrate over which plasma is generated is not lessthan 0.1 mm, whereby the plasma is assured of stability against ionbombardment.

In order to embed the electrode in the dense ceramic substrate, aceramic producing step, as will be mentioned later, must be implemented.The electrode, which has gone through the above ceramic producing stepundergoes some undulation in its profile. As a result, the thickness ofthe electromagnetic wave permeation layer between the electrode and thesurface of the substrate changed depending on where the electrode wasembedded flat. The magnitude of this change depends upon the accuracy ofthe production, and upon the materials, etc. in the case of the ordinaryproducing process. The change in the thickness of the electromagneticwave permeation layer reaches as much as 0.7 mm at the maximum. Sincethe thickness fluctuation of the electromagnetic wave permeation layerdepends on the plane location where the electrode is, it is necessarythat the minimum thickness of the electromagnetic wave permeation layerbe set at not less than 0.1 mm.

The inventors further proceeded with the investigation of theconstruction of the plasma generating electrode device. As a result, itwas found that, with the electrode-embedded article according to thepresent invention, as the embedded plane electrode comprises a metalbulk, the electrode exhibits a small resistance. In this regard, asupplementary account is give hereunder. Namely, since a screen printelectrode has a thickness of approximately some ten μm at most, theresistance inevitably increases.

Besides, since the substrate enclosing the electrode is a jointface-free monolithic sinter, discharge and dielectric breakdown do notoccur from the joint face even under the condition of high vacuum or thelike in which discharge likely occurs. As a consequence, the reliabilityof the electrode-embedded article is remarkably improved.

Further, the electrode-embedded article according to the presentinvention can be produced by hot press-sintering the ceramic moldingwith the planar electrode of a metal bulk embedded therein, whileapplying pressure to the molding in the thickness direction of theelectrode. In addition, this process has a lesser number of theproducing steps, and is devoid of a bonding step using silver solder orthe like, so that the process is suited for mass production.

The inventors further investigated the cause of damage to theelectromagnetic wave permeation quartz window in the ECR plasma unit. Asa result, the inventors came to reach the following conclusion. Namely,since the plasma generating reaction is a vigorous reaction, it is verydifficult to control the characteristics of the plasma with variousexternal parameters. Besides, since the ECR plasma has greatly intensiveenergy, component members exposed to the ECR plasma are liable to incurchanges in quality. Particularly with the ECR plasma unit, theplasma-generating position is controlled with the magnetic field.However, since the magnetic field is spatially non-uniform, the plasmaintensity is greatly fluctuated locally.

As a result, it is considered that the plasma ion bombardment againstthe electromagnetic wave permeation window will heat the surface of thewindow at a high temperature, and a silica glass window may sometimesundergo local melting. Such a phenomenon was likewise observed in therespective cases where a non-corrosive gas such as argon, nitrogen,oxygen, SiH₄ or the like was used.

Meanwhile, since the electromagnetic wave permeation window is exposedto the microwaves, a dielectric loss generates heat. In this way, theelectromagnetic wave permeation window incurs two different kinds ofthermal stresses, one stemming from a plasma thermal input to the windowand another resulting from self heat generation with the microwaves.Further, it was found that in the case where halogen-based non-corrosivegas such as ClF₃, NF₃, CF₄, CHF₃, SiH₂ Cl₂ or the like was used, thesurface of the electromagnetic wave permeation window surface reactedwith the halogen, and was etched, in addition to melting at the abovehigh temperature.

The inventors attempted to produce the electro-magnetic wave permeationwindow, using aluminum nitride exhibiting said property. As a result, itwas discovered that the electromagnetic wave permeation window washardly melted or broken owing to the above heat generation, and that thewindow scarcely underwent etching, with the halogen-based corrosive gas.In addition, it was likewise ascertained that aluminum nitride with saidproperty has great thermal shock resistance, the electromagnetic wavepermeation window was not broken even when the window temperature wentup locally with the microwaves passing therethrough. The presentinvention was completed based on the above.

Particularly, the wafers for use in the production of DRAMs increasetheir diameters. With this taken into account, it is necessary toincrease the diameters of the electromagnetic wave permeation windows.In this case, the electromagnetic wave permeation window could be stablyused by employing aluminum nitride as its material.

Thermal shock resistance ΔTc is defined as follows: For the test, a JIStest piece having the dimensions of 3 mm×4 mm×40 mm is used. This testpiece is brought into an electric furnace in which the test piece isheld for 10 minutes at an optional temperature. Thereafter, the testpiece is put into water at a temperature of 26° C. in an amount of 10liters to cool it quickly. Afterward, the 4-point bending strength ofthe test piece is measured at room temperature. As a result, the 4-pointbending strength of the test piece declines via a certain temperaturedifference as a border. Here, this temperature difference (maximumtemperature difference within which the 4-point bending strength doesnot fall) as the border is taken as ΔTc.

Aluminum nitride is known a corrosion resistant ceramic. It must beunderstood, however, that the corrosion resistance of this ceramicrepresents the ion reactivity with acid and alkaline solutions.Meanwhile, the present invention is concerned not with the ionreactivity but with the local heat generation due to the bombardment ofplasma ions. The present invention likewise is directed to thereactivity of halogen corrosive gases with plasma.

Examining a damaged electromagnetic wave permeation window of sapphirerevealed that the source of damage was located at the window surfacewhich had been exposed to the bombardment with plasma irons. Therefore,it suffices if at least that surface part of the electromagnetic wavepermeation window which is exposed to plasma is made of aluminum nitridehaving excellent thermal shock resistance and excellent corrosionresistance.

The electrode-embedded article according to the present invention ispreferred as an electric dust collector, an electromagnetic shield, ahigh-frequency electrode, and an electrostatic chuck. Particularly wherethe electrode-embedded article is fabricated as a high-frequencyelectrode for example, comprising tungsten, and the frequency is 13.56MHz, the thickness of the electrode is preferably not less than 430 μm.However, it is difficult to form the electrode in the thicknessspecified above by using the screen printing process. Further, when theelectrode-embedded article is applied as an electrostatic chuck or anelectric dust collector, the response speed in chucking and dustcollecting can be increased by making the electrode from the planarmetal bulk.

In case where the electrode-embedded article is installed in asemiconductor device production unit using the halogen-based corrosivegas, said electrode-embedded article provide the following function.That is, in the electrostatic chuck as illustrated in FIG. 3, it wassometimes observed that the filmy electrode 9 underwent corrosion withthe halogen-based corrosive gas. Further, since the filmy electrode 9was fabricated of a heavy metal-containing solder, it was feared thatthe semiconductors would suffer contamination with a heavy metal.

However, according to the present invention, since the substrateenclosing the electrode is a joint face-free monolithic sinter, thecorrosion of the electrode and the contamination inside thesemiconductor device production unit can be prevented. Thoseelectrode-embedded articles installed inside the semiconductor deviceproduction units using the halogen-based corrosive gas includes theelectrostatic chuck and the high-frequency electrode.

Nitride-based ceramics such as silicon nitride, aluminum nitride, boronnitride, SIARON, etc., silicon carbide, and an alumina-silicon carbidecomplex compound are ceramics desired to fabricate the substrate for theelectrode-embedded article of the present invention. Through theinvestigation the inventors revealed that from the viewpoint of thermalshock resistance, silicon nitride is most preferred, and also that fromthe standpoint of corrosion resistance, aluminum nitride is mostpreferable.

However, aluminum nitride is particularly hard to be sintered.Therefore, it is difficult to provide a sinter with relatively highdensity by the conventional sintering process under normal pressure.Thus in the past, to promote the sintering of aluminum nitride, a largequantity of a sintering aid used to be included in aluminum nitridepowder. However, such sintering aid becomes an impurity when theelectrode-embedded article is put particularly within the semiconductordevice production unit. This may cause contamination of thesemiconductor. In the process of producing the electrode-embeddedarticle according to the present invention, since the substrate withremarkably high relative density of more than 99% can be produced byhot-press sintering the aluminum nitride powder, even where the contentof impurities involved in the aluminum nitride powder is less than 1%.Dense aluminum nitride ceramic with a relative density of over 99%,which is produced by sintering under normal pressure, hotpress-sintering or the thermal CVD process, is desired.

In case where the electrode-embedded article according to the presentinvention is used as an electrostatic chuck and where the electrostaticchuck is used within the semiconductor device production unit, thefollowing problem occurs. Since ceramics have such a characteristic thattheir volume resistivities decline as the temperature rises, the currentflowing a semiconductor wafer attracted on the substrate increases withrise in temperature, whereby the wafer may be damaged. Therefore, it isdesired that the volume resistivity of the substrate be not less than10¹¹ Ωcm. In this regard, it is also desired that the substrate shows avolume resistivity not less than 10¹¹ Ωcm even in a high temperaturerange of, for example, 500°-600° C. when the substrate is used at hightemperatures not less than 600° C. To meet this requirement, alumina,beryllia, magnesia, silicon nitride, and boron nitride are preferred.

In the process of producing the electrode-embedded article according tothe present invention, a planar electrode comprising a metal bulk isembedded in a ceramic molding. For this steps, the following methods maybe recited by way of example.

Method (1): A pre-molded substrate is prepared, and said electrode isset thereon. Thereafter, ceramic powder is filled up on the pre-moldedsubstrate and electrode, followed by uniaxial pressing.

Method (2): Two planar molding are prepared through cold isostaticpressing and an electrode is held between these two planar moldings.Thereafter, said two moldings and the electrode are hot-pressed. In thismethod, the molding prepared via cold isostatic pressing exhibits ahigher density already at this stage and a lesser fluctuation in densityinside the molding, compared with Method (1). Accordingly, compared withthe Method (1), Method (2) gives a smaller shrinkage of the moldingduring hot press, and the lesser fluctuation after the sintering.Accordingly the mean dielectric strength of the substrate increasesrelatively.

The above-quoted functions and effects come to carry great significancewhen the electrode-embedded article is applied as an electrostaticchuck. This is because due to the above reasons, the mean dielectricstrength of a dielectric layer of the electrostatic chuck can be furtherincreased, and the reliability thereof can be remarkably improved.

In this sense, it is most desired that the relative density of themolding obtained by the cold isostatic pressing be not less than 60%.

In case where the electrode is screen-printed on the surface of amolding formed by the cold isostatic pressing, the print electrode isrequired to be degreased for a long time within a non-oxidizingatmosphere after the screen-printing. Therefore, the method wherein theelectrode is held between a pair of the moldings prepared by way of thecold isostatic pressing, is devoid of such a degreasing step for a longtime, and therefore, is advantageous from the standpoint of massproduction.

Further, assuming that the electrode film has been formed by the screenprinting where the electrode-embedded article is applied as anelectrostatic chuck, it is considered that the electrode film isdeformed during the hot press, whereby the thickness of the dielectriclayer lying on the electrode film becomes non-uniform. Meanwhile, theelectrode comprising a planar metal bulk is embedded as in the presentinvention, when the electrode is prevented from being deformed whenhot-pressed, since the electrode has rigidity. Thus, the non-uniformthickness of the dielectric layer can be prevented. Particularly whenthe electrode-embedded article is an electrostatic chuck, the chuckingperformance depends on the thickness of this dielectric layer. Thus, thethickness of the dielectric layer is important. The planar metal bulk inthe present invention refers to a monolithic planar configuration asshown in FIGS. 9 and 13 by way of example, without a wire or strip beingarranged in a spiral or zigzag form.

In the process of producing the electrode-embedded article of thepresent invention, the electrode is hot-pressed in the thicknessdirection thereof. Therefore, in order to prevent the electrode fromsuffering strain during hot pressing, the electrode is preferable of aflat plate configuration. In the case where the electrode is used wherethe temperature rises at not less than 600° C. at the maximum, it isdesired that such an electrode be made of a metal with a high meltingpoint. The electrostatic chuck is recited as such an application.

As such metals showing high melting points, tantalum, tungsten,molybdenum, platinum, rhenium, hafnium, and alloys of these metals maybe recited. From the standpoint of preventing the contamination of thesemiconductors, tantalum, tungsten, molybdenum, platinum, and the alloysthereof are preferable.

When the electrode is of tungsten and the substrate of silicon nitride,the coefficient of thermal expansion largely differs between them.Therefore, owing to mismatch between them in the thermal expansion, theintegration thereof was difficult by the conventional process in whichthe electrode film is prepared by screen printing, followed by sinteringunder normal pressure. Meanwhile, in the producing process according tothe present invention, the electrode and the substrate can be unitedeven if the coefficient of thermal expansion largely differs between theelectrode and the substrate. This is because the substrate molding ishot-pressed in the thickness direction of electrode.

The electrode involves a planar electrode made of a plate with numeroussmall holes in addition to a planar electrode comprising a thin plate.In case where the electrode is of a plate-like member with numeroussmall holes, since ceramic powder flows into these numerous small holesand reaches the rear side, the adhesion force of ceramic on both sidesof the plate-like member increases to enhance the mechanical strength ofthe substrate.

As such a plate-like member, a punched metal and a metal screen may berecited. In the case where the electrode is of a high melting pointmetal as punched, it is difficult to punch a large number of small holesin the high melting point metal, because such a metal has high hardness.Thus, the production cost remarkably goes up.

Meanwhile, when the electrode is of a metal mesh, it is easy to procurewires having a high melting point. Therefore, the metal mesh can beproduced by braiding such wires so that the electrode can be easilyproduced.

When such an electrode comprises a thin plate, it is observed that thedifference, in coefficient of thermal expansion between the electrodeand substrate causes large stress to be applied at a peripheral part ofthe electrode, whereby the substrate sometimes suffers damage due tothis stress. But, when the electrode is of the plate-like member havingnumerous small holes, these small holes disperse the stress.

In the electrode-embedded article of the present invention, noparticular restriction is imposed on the mesh pattern of the metalscreen and the diameter of the wire. However, the wire diameter of 0.03mm and the mesh size of 150 through the wire diameter 0.5 mm and themesh size 6 gave rise to no problem in use. The sidewise cross sectionsof the wire making up the metal screen may be of various rolled profilessuch as circular, elliptical or rectangular.

With the plasma generating electrode device of the present invention,for the above reasons taken with the thickness fluctuation of theelectromagnetic wave permeation layer, it is desired that the averagethickness thereof be not less than 0.5 mm.

In case with the plasma generating electrode device of the presentinvention, the dielectric constant of the electromagnetic wavepermeation layer is generally large. However, the excess averagethickness of the electromagnetic wave permeation layer coincides withthe increased quantity of self heat generation due to the loss of thedielectric layer of the electromagnetic wave permeation layer.Consequently, the efficiency of plasma energy tends to decrease. Fromthis viewpoint, it is particularly desired that the average thickness ofthe electromagnetic wave permeation layer be not more than 5.0 mm.

In case where the plasma generating electrode device of the presentinvention is used in a semi-conductor device production unit with use ofthe halogen-based corrosive gas so as to generate plasma by applyinghigh-frequency electric power to the halogen-based corrosive gas, areaction product is formed on the surface of the electromagnetic wavepermeation layer due to the bombardment with ions of the halogen-basedcorrosive gas. As the thickness of this reaction product layer reaches afew μm to some tens μm, the minimum thickness of the electromagneticwave permeation layer needs to be not less than 0.1 mm, and also thatthe average thickness thereof is preferably not less than 0.5 mm so thatsufficient insulating property may be maintained.

Where the electromagnetic wave permeation layer is formed, usingaluminum nitride with a relative density of not less than 99% in theplasma generating electrode device of the present invention, an AlF₃passivation layer is formed as a reaction product layer. Since the AlF₃passivation layer has a corrosion resistive action, corrosion can beprevented from propagating inwardly beyond this layer.

Particularly when the plasma generating electrode device is used insemiconductor device production units, it is essential to prevent thesemiconductors from undergoing contamination with a metal. With anincreased densification progress, the demands calling for theelimination of the metal have recently increased. Taking into accountsuch demands, it is desired that the content of impurities in aluminumnitride be restricted to below 15%.

With the plasma generating electrode device of the present invention, itis desired that the electrode be a bulk-like planar electrode, and thatthe substrate enclosing the planar electrode be a joint face-freemonolithic sinter. The planar metal bulk refers to a monolithic planarmold, without a wire or a strip being arranged in a spiral or zigzagform. This will be further explained.

According to the method in which the plasma generating electrode deviceis produced by forming a print electrode on a ceramic green sheet,laminating another green sheet on the former, and press molding andfiring the laminate, the print electrode is displaced at a press-moldingstage or a firing stage. The result is that the electromagnetic wavepermeation layer is liable to undergo fluctuation in its thickness, nomatter how fine the surface of the dielectric layer is planed. Moreover,according to the sintering process under normal pressure, it isdifficult to secure the dielectric layer at 100% denseness particularlywhen the size of the plasma generating electrode device increases.Consequently, reliability falls from the standpoint of preventing thedielectric breakdown. On the other hand, the size of semiconductorwafers has been increasing. For sufficient permeability of high-frequentwaves, it is necessary to reduce the reactance component of the plasmagenerating electrode device, and it is likewise required to suppress theelectrode resistance below 1Ω. For this purpose, the electrode thicknessneeds to be increased sufficiently. But, this is difficult for the printelectrode.

If an embedded planar electrode is made of a metal bulk, it is easy toreduce the resistance of the electrode. The screen print electrode has athickness of some tens μm at the maximum, and therefore, the resistancethereof inevitably increases. In case where the electrode is made oftungsten and the frequency is 13.56 MHz, it is desired that theelectrode thickness be not less than 20 μm. However, it is difficult toform the electrode of such a thickness by the screen printing process.

Besides, since the substrate enclosing the electrode is a jointface-free monolithic sinter, electric discharge and dielectric breakdownoccur from such a joint face under the condition such as vacuum in whichdischarge is likely to occur. As a result, the plasma generatingelectrode device has its reliability remarkably improved.

Where the plasma generating electrode device is installed in asemiconductor device production unit using a halogen-based corrosivegas, the high-frequency electrode is liable to be corroded with thehalogen-based corrosive gas. Further, since the high-frequency electrodeis made of a metal-contained solder, it is feared that the semiconductormay undergo contamination with a solder metal. In this case, however, ifthe substrate enclosing the electrode is made up in the form of a jointface-free monolithic sinter, corrosion of the electrode and thecontamination inside the semiconductor device production unit can beprevented.

As the ceramics constituting the substrates, nitride-based ceramics suchas silicon nitride, aluminum nitride, boron nitride, and SIARON, andalumina-silicon carbide composite material are preferred. According tothe inventors' investigation, from the viewpoint of thermal shockresistance, silicon nitride is particularly preferred, while aluminumnitride is preferred from the corrosion resistance against thehalogen-based corrosive gas.

The plasma generating electrode device of the present invention can beproduced by the afore-mentioned Method (1) or (2).

When used in condition that the temperature rises particularly at hightemperatures less than 600° C., the high-frequency electrode of theplasma generating electrode device of the present invention ispreferably made of a metal of a high melting point. As such a highmelting point metal, tantalum, tungsten, molybdenum, platinum, rhenium,hafnium, and the alloys thereof may be used. When the plasma generatingelectrode device is installed within the semiconductor device productionunit, tantalum, tungsten, molybdenum, platinum, and the alloys thereofare preferred from the standpoint of preventing contamination of thesemiconductor.

With the plasma generating electrode device of the present invention,the electrode includes a planar electrode composed of a thin plate and aplanar electrode made of a plate with numerous small holes. When theelectrode is the planar type electrode with numerous small holes,ceramic powder flows into these small holes, and moves to the rear face.Consequently, the substrate has its mechanical strength increased onopposite sides of the planar member.

As the plate-like members, a punched metal and a metal screen may berecited. In case that the electrode is made of the high melting pointmetal as punched, it is difficult to punch a large number of small holesin the high melting point metal, because the metal is very hard.Consequently, the production cost remarkably goes up.

Meanwhile, when the electrode is a metal electrode, it is easy toprocure wires made of a high melting point, so that the mesh electrodecan be easily produced by braiding the wires. Thus, the electrode can beeasily produced.

When the electrode is of a thin plate, a particularly large stressoccurs in the peripheral edge portion of the electrode due to differencein coefficient of thermal expansion between the electrode and thesubstrate, so that the substrate sometimes is damaged by this stress.However, when the electrode is of a planar member having a number ofsmall holes, the above stress is dispersed by these numerous smallholes. In addition, when the electrode is a mesh electrode, the meshelectrode is formed by the wires and the section of the wires iscircular. Thus, the effect of dispersing the stress becomes greater.

No particular limitation is posed upon the mesh shape, the wirediameter, etc. of the mesh electrode. However, it is preferable that thewire width of the mesh electrode is not more than 0.8 mm and that notless than 8 wires cross per inch. That is, if the wire width is morethan 0.8 mm, the electric field intensity distribution in theplasma-generating space defined by the opposite electrodes is disturbedso that the plasma distribution may be likely to be deteriorated.Further, when the plasma generating electrode unit is used for a longtime, the stress field formed by the wires present as a foreign matterin the ceramic exceeds the strength of the ceramic, the ceramic tends tobe broken. Furthermore, if the number of the crossing wires per one inchis less than 8, current is unlikely to uniformly flow the entire meshelectrode. From the standpoint of the practical production, it ispreferable that the wire width of the mesh electrode is not less than 1mm and the number of the crossing wires per one inch is not more than100.

The widthwise cross sectional shape of the wires constituting the meshelectrode may be of a circular shape or any of various rolled shapessuch as an elliptical shape and rectangular shape.

In the plasma generating electrode unit according to the presentinvention, heat may be generated at that surface of the substrate on theplasma generating side by embedding the resistance heat generator madeof a high melting point metal in the substrate and feeding electricpower to the resistance heat generator. By so doing, the wafer can bedirectly heated in the state that the wafer is placed and held directlyon the plasma generating electrode unit. Thus, response at the time ofuniform heating and heating can be improved. In the plasma generatingelectrode unit, at least the electromagnetic wave permeation layer inthe substrate may be formed of aluminum nitride having the dielectricloss tan δ of not more than 10⁻² and the thermal shock resistance ΔTc ofnot less than 250° C.

The function and the effects of aluminum nitride constituting theelectromagnetic wave permeation layer are the same as those of theabove-mentioned electromagnetic wave permeation body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating the construction of one example of aconventional heating unit;

FIG. 2 is a view illustrating the construction of another example of theconventional heating unit;

FIG. 3 is a cross sectional view for outlining one example of aconventional electrostatic chuck;

FIG. 4 is a schematic view for schematically illustrating how aresistance heating element is embedded in the substrate of the plasmagenerating electrode device according to the present invention;

FIG. 5 is a schematic view for schematically illustrating theconstruction of one embodiment of the heating unit incorporating theplasma generating electrode device 14 with a heater shown in FIG. 4;

FIG. 6 is a cross sectional view for outlining an electrostatic chuck asan electrode-embedded article, and an mechanism for measuring the forceof attraction of the chuck;

FIG. 7 is a partial cross sectional view for schematically illustratinghow the plasma generating electrode device 41 according to the presentinvention is installed within a semiconductor device production unit;

FIG. 8 is a perspective view for illustrating the electrostatic chuck inFIG. 6 or the plasma generating electrode device 41 with a part thereofbeing cut away;

FIG. 9 is a perspective view for illustrating a mesh electrode or mesh30 usable as a high-frequency electrode or an electrostatic chuckelectrode;

FIG. 10(a) is a schematic cross sectional view for illustrating themolding step in uniaxial press mold, FIG. 10(b) a cross section view ofa molding 53, and FIG. 10(c) a cross section view for outlining a mainpart of electrostatic chuck 36 or a plasma generating electrode device41;

FIG. 11 is a cross sectional view of a molding prepared by the coldisostatic pressing process;

FIG. 12(a) is a perspective view of a punched metal 64 to be used as ahigh-frequency electrode or an electrostatic chuck, FIG. 12(b) is aperspective view of a circular thin plate 65 usable as a high-frequencyelectrode or an electrostatic chuck, and FIG. 12(c) is a plan view of athin plate 66 to be used as a high-frequency electrode or anelectrostatic chuck;

FIG. 13 is a partial cross section view for schematically typicallyillustrating how the plasma generating electrode device 60 according toa further embodiment of the present invention is installed within thesemiconductor device production unit; and

FIG. 14 is a schematic view for illustrating the concept of theconstruction of an electronic cyclotron resonance plasma generator towhich the electromagnetic wave permeation body of the present inventionis applicable.

BEST MODE OF PERFORMING THE INVENTION

FIG. 4 is a schematic view for illustrating the structure of theheater-equipped plasma generation electrode unit 14 according to thepresent invention. According to the embodiment illustrated in FIG. 4, aresistance heat generating body 19 made of a high melting point metalsuch as W or Mo is embedded inside a ceramic substrate 18 having, forexample, a discoidal shape. This heat generating body 19 is preferablyspirally coiled, and arranged in a swirling form when the discoidalceramic substrate 18 is viewed in plane. At opposite ends of theresistance heat generating body 19 are provided terminals 20A, 20B forthe supply of electric power, to which electric cables 21 are continued.Inside the ceramic substrate 18 above the resistance heat generatingbody 19 is provided a discoidal plasma generating electrode 15 having adiameter slightly smaller than the ceramic substrate 18. To the plasmagenerating electrode 15 is provided a terminal 22 and a succeeding cable23 for the supply of high frequency electric power. Only a necessary setof such terminals 22 and succeeding cables 23 (one set in thisembodiment) are provided depending upon high frequency signals to besupplied.

Since the ceramic substrate 18 is heated at 600° C. to 1100° C. at themaximum in, for example, a hot CVD unit, the substrate is preferablymade of alumina, a silicon nitride sinter, sialon, silicon carbide,aluminum nitride, or an alumina-silicon carbide composite material fromthe standpoint of heat resistance. Particularly, the ceramic substrate18 is preferably made of non-oxide type ceramic. This is because thenon-oxide type covalent ceramic such as SiC, Si₃ N₄ or AlN generates asmaller amount of a gas under high vacuum as compared with oxide typeceramics such as alumina. Among them, silicon nitride is preferred,because when silicon nitride is used, the strength of the entire plasmagenerating electrode unit 14 becomes higher, its coefficient of thermalexpansion is almost equal to that of silicon as a typical material forwafers, and silicon nitride has high durability against the corrosivegas.

In order to embed a plasma electrode in the ceramic substrate 18, thesubstrate 18 is constituted by an electromagnetic wave permeation layeror a filmy substrate 16 and a planar substrate 17. The components 16, 17may be made of the same material or different kinds of materials. Inorder to avoid an effect upon a semiconductor device due to currentflowing a wafer, the electromagnetic wave permeation layer 16 preferablyhas a volume resistivity of not less than 10⁸ Ωcm and a thickness of notless than 10 μm. The filmy substrate 16 is placed in the plasma sheath,and undergoes ion bombardment with molecules activated upon applicationof bias voltage to the electrode 15. For this reason, ion bombardmentresistance is required for the electromagnetic wave permeation layer 16,so that its thickness is preferably set at not less than 100 μm.However, as the electromagnetic wave permeation layer 16 becomesthicker, dielectric loss occurs upon application of the high frequencypower. Consequently, the loss of high frequency power increases, and theefficiency of the high frequency power decreases. Accordingly, thethickness of the electromagnetic wave permeation layer 16 is preferablynot more than 1 mm. Further, the electromagnetic wave permeation layer16 and the substrate 17 are monolithically molded. Alternatively, thelayer 16 and the substrate 17 may be joined with borosilicate glass oroxynitride glass as an insulating joining material. A reactancecomponent of the electrode 15 needs to be decreased so as to assuresufficient transmission of high frequency waves, and the electrode 15needs to have a sufficient thickness to present not more than 1Ω ofresistance. For this purpose, when the electrode 15 is made of tungstenor molybdenum, its thickness needs to be not less than 8 μm.

FIG. 5 is a schematic view for illustrating an example of the structureof a heater unit into which the plasma generating electrode unit 14 ofFIG. 4 is incorporated. In the embodiment of FIG. 5, the plasmagenerating electrode unit 14 is installed, via an arm 3, inside achamber 1 to be exposed to a deposition gas or the like. At that time,the plasma generating electrode unit 14 is so installed that the plasmagenerating electrode 15 may be located near the upper face, and a waferW is placed on the upper face of the plasma generating electrode unit14. A pair of an electric power supply cables 21 and a high frequencysignal supply cable 23 are arranged to communicate with the exterior ofthe chamber 1. In this state, electric power is supplied via a pair ofthe cables 21 for heating the resistance heating element 19, whereas ahigh frequency signal is supplied via the cable 23 for generating plasmaat the electrode 15. Thus, heating and plasma generation can beeffected. The plasma generating electrode unit is not limited to theabove-mentioned embodiment only, but various modifications andvariations are possible. For example, although in the above embodiment,the electrode 15 is used only as an electrode for the generation ofplasma, this electrode 15 may be simultaneously operated as anelectrostatic chuck electrode to chuck the wafer W based onelectro-static capacity. For example, when the electrode 15 issimultaneously supplied with DC voltage for providing electrostaticcapacity as well as with high frequency signals via an insulatingtransformer, the wafer W can be attracted onto the upper face of theplasma generating electrode unit 14 and plasma can be simultaneouslygenerated. In order to supply the high frequency signals, at least fourcables having a diameter of 10 mm are necessary when each cable is madeof tungsten and has a resistance of not more than 1Ω. Thus, this largelydiffers from the case where the resistance may be 0 to several hundred Ωand the diameter of around 0.1 mm when the electrode 15 is used as theelectromagnetic electrode only.

FIG. 6 is a sectional view for outlining an electrostatic chuck. FIG. 7is a partially sectional view for schematically illustrating the statethat plasma generating electrode unit 41 is installed in the chamber 1.FIG. 8 is a partially cut perspective view for illustrating theelectrostatic chuck of FIG. 6 or the plasma generating electrode unit 41of FIG. 7. FIG. 9 is a perspective view of a metal mesh 30. FIG. 10(a)is a schematically sectional view for illustrating the molding step inthe uniaxial press mold, FIG. 10(b) is a sectional view illustrating amolding 53, and FIG. 10(c) is a sectional view for outlining theelectrostatic chuck or the plasma generating electrode unit. FIG. 11 isa sectional view for illustrating a molding prepared by the coldisostatic pressing.

In order to produce the electrostatic chuck 36 in FIG. 6 or the plasmagenerating electrode unit 41 in FIG. 7, a press molding machine shown inFIG. 10(a) is first prepared. A mold frame 49 is engaged with a lowermold 52 of the press molding machine. Ceramic powder is filled into aninner space 48 of the mold frame 49, and uniaxially press molded betweenthe lower mold 52 and an upper mold not shown to obtain a pre-moldedbody 51A. Then, a metal mesh 30 is placed on the pre-molded body 51A. Asshown in FIG. 9, the metal mesh 30 has a circular shape. In FIG. 9, 46and 47 denote a mesh and a wire, respectively.

Next, ceramic powder 50 is filled on the metal mesh 30 to bury the metalmesh 30. The powder 50 is uniaxially press molded by the upper mold notshown, thereby producing the molding 53 shown in FIG. 10(b). In themolding 53, the metal mesh 30 is embedded between the pre-molded body51A and a pre-molded body 51B. Then, this molding 53 is subjected to hotpress sintering and a given polishing. Thereby, a main body of theelectrostatic chuck 36 or the plasma generating electrode unit 41 isobtained as shown in FIG. 10(c).

In FIG. 10(c), a ring-shaped flange 31c is provided at a peripheral sideface 31b of a substantially discoidal substrate 31, and an electrostaticchuck electrode 29 or a high frequency electrode 55 made of the metalmesh 30 is embedded inside the substrate 31. A dielectric layer 34 or anelectromagnetic wave permeation layer 37 is formed in a given thicknesson a side of a setting face 31a for an object to be fixed, such as asemiconductor wafer. A terminal 33 or 38 is buried on a side of asupporting portion 35, and is connected to the electrode 29 or 55. Anend face of the terminal 33 or 38 is exposed through a rear face 31d ofthe substrate.

According to another process, the ceramic powder 50 is molded by thecold isostatic press to produce planar moldings 56A and 56B as shown inFIG. 11. Then, a metal mesh 30 is held between the moldings 56A and 56B,which are subjected to the hot press sintering as they are.

The electrostatic chuck 36 shown in FIGS. 6 and 10 was produced by theabove process. First, powdery aluminum nitride containing 5% by weightof yttria was used as the ceramic powder 50. The powder was molded underpressure of 7 tons/cm² by the cold isostatic pressing, thereby producingtwo moldings 56A and 56B. The bulk density of each molding was 2.51g/cm².

The metal mesh made of metallic molybdenum was prepared. The metal mesh30 was a rolled product having a mesh size of 0.18 mm in diameter. Thismetal mesh was held between the moldings 56A and 56B, which was hotpress sintered at 1900° C. under 200 kg/cm². Thereafter, the averagethickness of the dielectric layer was adjusted to 300 μm on the averageby machining. The thickness of the dielectric layer 34 actually measured306±50 μm. Then, a hole was bored from the rear face by ultrasonicworking, and terminal 33 was joined thereinto. In the substrate 31 atfour locations were bored holes 32 into which are passed pins forsupporting the semiconductor wafer.

This electrostatic chuck 36 was subjected to an operation test. Anelectric wire 27 was connected to the terminal 33, a stainless weight 26was placed on the setting face 31a, and an electric wire (earth wire)was contacted with the stainless weight 26. The electric wires 27 wereconnected to a DC power source 28. The stainless weight 26 was connectedto a load cell 25 for the measurement of a load. Voltage of 1 KV wasapplied to make the stepping motor 24 to pull up the stainless weight 26connected to the load cell 25 in an arrow A direction. The attractionforce was determined according to (a load when the load cellpeeled--mass of the weight)/(sectional area of an attracted face of theweight). As a result, the attraction force was 50 g/cm².

The relative density of the substrate 31 was not less than 99.9%, andthe minimum insulating resistance and the average insulating resistancewere 10 KV/mm and 28 KV/mm, respectively, within a plane of 146 mm indiameter.

On the other hand, the conventional electrostatic chuck made ofpressurelessly sintered aluminum nitride exhibited the bulk density of99.0% at the maximum. The minimum insulating resistance and the averageinsulating resistance were 3 KV/mm and 15 KV/mm, respectively, within aplane of 150 mm in diameter.

In the semiconductor production unit shown in FIG. 7, the plasmagenerating electrode unit 41 is installed in the chamber 1 via the arm3. At that time, the plasma generating electrode unit 41 is so installedthat the high frequency electrode 55 may be located on the side of theupper face of the unit, and the wafer W is placed on the setting face31a. One end of an electric power-supplying cable 43A is connected tothe terminal 38, and the other end of the cable 43A is extended outsidethe chamber 1 and connected to a high frequency electric power source44. An opposite electrode 42 is arranged at a location opposed inparallel to the high frequency electrode at a given interval. One end ofthe electric power-supplying cable 43B is connected to the oppositeelectrode 42, whereas the other end of the cable 43B is extended outsidethe chamber 1 and connected to the high frequency electric power source44 and earth 45. In FIG. 7, "t" is the thickness of the electromagneticwave permeation layer 37.

In this state, plasma can be generated in the plasma-generating area 39above the wafer W by supplying the high frequency electric power througha pair of the cables 43A and 43B. At this time, a plasma sheath 40 isgenerated between the plasma generating area 39 and the setting face31a.

FIG. 12(a) is a perspective view for illustrating a punched metal 64 tobe effectively used as a high frequency electrode or an electrostaticchuck electrode. The punched metal 64 has a circular shape, and isformed with a number of round holes 64b in a grid pattern within acircular flat plate 64a.

FIG. 12(b) is a perspective view for illustrating a circular thin plate65 to be effectively used as a high frequency electrode or anelectrostatic chuck electrode. FIG. 12(c) is a plane view forillustrating a thin plate 66 to be effectively used as a high frequencyelectrode or an electrostatic chuck electrode. In the thin plate 66,totally six parallel straight slender cuts 66b, 66c are formed. Amongthem, three cuts 66b are opened on the lower side in FIG. 12(c), whereasthe remaining three cuts 66c are opened on the upper side in FIG. 12(c).The cuts 66b and the cuts 66c are alternatively arranged. By employingsuch a configuration, a slender electrically conductive path is formedin the thin plate. Therefore, terminals 66a are connected to oppositeends 66 of the electrically conductive path, respectively.

FIG. 13 is a partially sectional view for schematically illustrating thestate in which a plasma generating electrode unit 60 according toanother embodiment is installed in the chamber 1 in the same manner asin the embodiment of FIG. 7. Same reference numerals are given to thesame constituent elements as shown in FIG. 7, and explanation thereon isomitted.

In the plasma generating electrode unit 60, a resistant heat generatingbody 61 made of a high melting point metal is embedded inside asupporting portion 35 of a substrate, that is, between the highfrequency electrode 55 and the rear face 31d. Opposite ends of theresistance heat generating body 61 are connected to terminals 62,respectively, and each of them is buried in the substrate 31 and exposedto the rear face 31d of the substrate 31. One end of an electricpower-supplying cable 63 is connected to respective one of the terminals62, and the other of the cable 63 is extended outside the chamber 1 andconnected to an electric power source not shown.

The resistance heat generating body is preferably constituted as a coilin which a wire or a strip is spirally coiled. The coil is embedded in asubstantially spiral or swirling form as viewed in plane from the sideof the rear face 31d or the setting face 31a. After the wafer W isplaced at a given position, the wafer can be heated by supplyingelectric power to the resistive heat generating body 61 simultaneouslywith the generation of plasma.

In the following, more concrete experimental results will be described.

(Experiment 1)

A plasma generating electrode unit 41 as shown in FIGS. 7 to 10 wasproduced. First, powdery aluminum nitride containing 0.1% of metallicimpurities other than aluminum was prepared as the ceramic powder 50.This powder was molded under pressure of 7 tons/cm² by the coldisostatic press, thereby producing two planar moldings 56A and 56B asshown in FIG. 11. The bulk density of each molding was 2.2 g/cm³.

A metallic molybdenum mesh or mesh electrode 30 was prepared. Thediameter of wires constituting the mesh electrode 30 was 0.35 mm with#24 (the number of crossing wires per one inch being 24) and the outershape of 200 mm in diameter. This mesh electrode 30 was held between themoldings 56A and 56B, which were subjected to hot press sintering at1900° C. under 200 kg/cm². By so doing, an aluminum nitride sinteredbody having the relative density of 99.4% was obtained.

When powdery aluminum nitride containing 5% of yttria was used in asimilar example, aluminum nitride sintered bodies having the relativedensity of not less than 99% were obtained by any of the uniaxial pressprocess and the hot press process.

Then, the surface of the substrate (a setting face 31a) was machined. Atthat time, while the thickness or the distance from the mesh electrode30 to the surface at each planar location was being measured by a filmthickness meter of an eddy current detecting system, the surface wasmachined. Thereby, the inclination of the mesh electrode 30 wascoincident with that of the surface of the electromagnetic wavepermeation layer 37 so that the center line of the mesh electrode 30might not be inclined with respect to the surface of the electromagneticwave permeation layer 37. Thereafter, a hole was bored in the substratefrom the rear side 31d by ultrasonic wave working, and a terminal 38 wasjoined thereto. The plasma generating electrode unit 41 had thedimensions of 12 mm in thickness and 205 mm in diameter. As shown inTable 1, the average thickness, the fluctuation in thickness, and theminimum thickness of the electromagnetic wave permeation layers 37 werevaried.

An 8-inch wafer was placed on the surface of each plasma generatingelectrode unit. Into the chamber 1 introduced CF₄ gas, and a gas feedsystem and a gas exhaust system were so controlled that the pressuremight be controlled to 400 mmTorr. As the high frequency power source,those having frequencies of 13.56 MHz and 2 kW, respectively, were used.In order to stabilize the discharging state, a machining box wasinserted between the electric power source and the high frequencyelectrode. The discharging state was evaluated according to threelevels. Results thereof are shown in Table 1.

                  TABLE 1                                                         ______________________________________                                              Average   Fluctu-  Max.   Min.                                          Test  thickness ation    thickness                                                                            thickness                                     No.   (mm)      (mm)     (mm)   (mm)    Judgment                              ______________________________________                                        1     0.3       0.8      0.8    0.01    X                                     2     0.5       0.8      0.9    0.1     ◯                         3     2         0.9      2.4    1.5     ◯                         4     5         1.0      5.5    4.5     ◯                         5     10        0.7      10.3   9.6     Δ                               ______________________________________                                    

In Test No. 1, the average thickness was 0.3 mm, but the mesh electrode30 was undulated. Thus, the minimum thickness was 0.01 mm to deterioratestability of the plasma sheath near a location having the minimumthickness in the plasma generating test. This is considered thatelectric charges passed at the surface of aluminum nitride underwentdielectric breakdown at a thin location for some reason, so that thesurface potential could not be kept constant, thereby changing thesheath area. In Test No. 2, no problem occurred in the stability of theplasma sheath.

In Test No. 5 with the average thickness "t" of 10 mm, the brightness ofplasma lowered, and the temperature of the electrode unit vigorouslyrose beyond 300° C. This is considered that the dielectric loss ofaluminum nitride decreased the electric field intensity of the surface,and further caused the self heat generation of the aluminum nitridelayer. Under this condition, no matter how well plasma is stabilized,the efficient of plasma power decreases and the temperature cannot besufficiently controlled. Consequently, the semiconductor wafer may bethermally damaged.

(Experiment 2)

In the same manner as in Experiment 1, plasma generating electrode unitswere prepared, except that the wire diameter of the mesh electrode 30and the number of wires per one inch were varied as shown in Table 2.

                  TABLE 2                                                         ______________________________________                                        Test   Wire diameter                                                                             No. of    Plasma                                           No.    (mm)        wires/inch                                                                              stability                                                                             Durability                               ______________________________________                                         2     0.35        30        ◯                                                                         ◯                             6     0.05        200       ◯                                                                         ◯                             7     0.1         120       ◯                                                                         ◯                             8     0.2         120       ◯                                                                         ◯                             9     0.2         30        ◯                                                                         ◯                            10     0.35        80        ◯                                                                         ◯                            11     0.35        15        ◯                                                                         ◯                            12     0.5          8        ◯                                                                         ◯                            13     0.8          8        ◯                                                                         ◯                            14     1.0          5        X       X                                        ______________________________________                                    

The mesh generally has the properties that the greater the diameter ofthe wires, the smaller is the number of wires per one inch, whereas thesmaller the diameter of the wires, the greater is the number of wiresper one inch. Therefore, for example, a mesh having the wire diameter of0.05 mm and the number of the wires per one inch being 5 cannot beproduced. Thus, almost all the meshes which can be readily produced inthe commercial base are recited in Table 2. With respect of each unit,plasma was generated and its stability was tested in the same manners asin Experiment 1. In each of the units of Test Nos. 2, 6 to 13, plasmacould be stably generated. Thus, they were indicated as "◯" in the item"Plasma stability" in Table 2. Further, it was observed that theirsubstrates were not damaged even in 48 hour holding. Thus, they wereindicated as "◯" in the item "Durability" in Table 2.

In Test No. 14, the mesh having the wire diameter of 1.0 mm and thenumber of wires per one inch being 8 was used, but localization was seenin the plasma distribution, and the substrate was damaged after thelapse of 3.5 hours.

(Experiment 3)

CF₄ is a halogen-based corrosive gas which generates fluorine radical toetch or clean various materials. In Experiment 1, various properties ofaluminum nitride constituting the electromagnetic wave permeation layerin Experiment 1 were measured. As a result, the dielectric loss tan δwas 0.6×10⁻³ (1 MHz), and the thermal shock resistance ΔT was 250° C.Further, with respect to the sample in Test No. 2, the surface of theelectromagnetic wave permeation layer was observed based on an EDAXchart and a scanning type electron micrograph. As a result, no changewas observed in the EDAX chart between before and after the test. Thescanning type electron micrograph seemed to reveal that aluminumfluoride was produced on the surface of the electromagnetic wavepermeation layer after the test. Therefore, since corrosion withfluorine radicals was suppressed by a passivation film of AlF₃, thecorrosion of the surface of the electromagnetic wave permeation layerwas prevented. It was also confirmed that no particle was formed in thepassivation film of AlF₃.

(Experiment 4)

With respect to Test No. 2 of the above Experiment 1, similarobservations were effected in the same manners as in Experiment 3 exceptthat the gas introduced into the semiconductor production unit waschanged to ClF₃, NF₃, Cl₂, SiH₂ Cl₂, or CF₃. In each case, resultssimilar to those in Experiment 3 were obtained. Therefore, it wasconfirmed that the plasma generating electrode unit according to thepresent invention is general-purpose for various halogen-based corrosivegases.

FIG. 14 is a schematic view for illustrating the concept of an electroncyclotone resonance (ECR) apparatus. Microwaves (generally 2.45 GHz) areirradiated through a waveguide 69 in an arrow D direction, permeates anelectromagnetic wave permeation window 70, and enters an inlet sideportion 72a of chamber 72. A solenoid coil 67 is installed to surroundthe outer peripheral side of the inlet side portion 72a of the chamber72. The coil 67 generates a magnetic field having an intensity of notless than 500 gauss.

A solenoid coil 77 is installed around the outer side of a processingchamber 75 of the chamber 72. The coil 77 spreads the magnetic field toconstitute a reflecting magnetic field. Around the periphery of theelectro-magnetic wave permeation window 70 is installed a water-coolingjacket 71 for preventing heating of a sealant which maintains thegas-tightness of the processing chamber 75, so the electromagneticpermeation window 70 is cooled. A gas is fed through a gas feed opening73 provided at the inlet side portion 72 in an arrow E direction. Thegas is discharged through a gas outlet 76 provided at an underside faceof the chamber 72 in an arrow B direction.

When microwaves are irradiated into the chamber 72, high frequencyvoltage in a microwave region is applied to the gas so that plasma isgenerated in the high frequency electric field having a spatiallynon-uniform intensity distribution and the static magnetic field. Thereflecting magnetic field applies downward force upon the generatedplasma, so that the plasma is accelerated downwardly in an arrow Cdirection.

A susceptor 74 is installed in a lower portion of the processing chamber75, and a wafer W is placed and held on the susceptor 74. The pressureinside of the chamber 72 is kept at a constant value.

By using this apparatus, an electromagnetic wave permeation window 70was made of aluminum nitride having the above-mentioned propertiesaccording to the present invention. As Comparative Example 1, anelectromagnetic wave permeation window 70 was made of quartz. AsComparative Example 2, an electromagnetic wave permeation window 70 wasmade of Al₂ O₃. Properties of each material are shown below.

                  TABLE 3                                                         ______________________________________                                        Properties of aluminum nitride                                                ______________________________________                                        4-point bending 400 MPa                                                       strength                                                                      Weibull coefficient                                                                           14                                                            Thermal conductivity                                                                          150 W/m · K                                                          (measured at room temperature)                                Specific heat   0.18                                                                          (measured at room temperature)                                Thermal impact  500° C.                                                resistance ΔTC                                                          Dielectric constant ε                                                                 8.6 (at room temperature, 10 MHz)                             Dielectric constant ε                                                                 8.8 (at room temperature, 1 MHz)                              Dielectric loss tan δ                                                                   (3.50-3.90) × 10.sup.-3                                                 (at room temperature 10 GHz)                                  Dielectric loss tan δ                                                                   2.5 × 10.sup.-3                                                         (at room temperature 1 MHz)                                   Visible radiation                                                                             3% t = 0.75 mm                                                transmittivity                                                                ______________________________________                                    

                  TABLE 4                                                         ______________________________________                                        Properties of quartz                                                          Thermal impact  1000° C. (provided, a wave trans-                      resistance ΔTc                                                                          mission loss occurs at 1200° C.)                       Dielectric constant ε                                                                 3.5-3.7                                                                       (at room temperature, 1 MHz)                                  Dielectric loss tan δ                                                                   1.5 × 10.sup.-4                                                         (at room temperature, 1 MHz)                                  Visible radiation                                                                             98%, t = 0.75 mm                                              transmittivity                                                                Properties of Al.sub.2 O.sub.3                                                Thermal impact  190-200° C.                                            resistance ΔTc                                                          Dielectric constant ε                                                                 10.6                                                                          (at room temperature, 1 MHz)                                  Dielectric loss tan δ                                                                   1.1-2.9 × 10.sup.-3                                                     (at room temperature, 1 MHz)                                  Visible radiation                                                                             95-96%, t = 0.75 mm                                           transmittivity                                                                ______________________________________                                    

The pressure inside the chamber 72 was held at 0.5 mTorr. As an etchinggas, CF₄ was fed, activated in the plasma, and fed onto the wafer W. Thesemiconductor wafer W having the dimension of 8 inches in diameter wasused. As the semiconductor becomes greater, the dimension of theelectromagnetic wave permeation window 70 needs to be increased. Forthis reason, the dimension of the electromagnetic wave permeation window70 was set at a diameter of 230 mm.

The susceptor 74 was made of aluminum nitride having the aboveproperties. The reason why aluminum nitride was used as the material isthat the material of the susceptor is required to not interrupt themagnetic fields of the coils 67 and 77 and to not change the flow of themicrowaves.

With respect to each case, etching was effected, and the surface stateafter the etching was observed visually, EDAX, a scanning type electronmicrograph. As a result, it was confirmed that the electromagnetic wavepermeation window 70 was free from damage or permeation loss with theECR plasma. That is, the surface was not melted with the ECR plasma.

Further, CF₄ generates fluorine radicals, which etches or clean variousmaterials. However, no change was observed in Example between before andafter the test. The scanning type electron micrograph seemed to revealthat aluminum fluoride was produced on the surface of theelectromagnetic wave permeation window. Therefore, since corrosion withfluorine radicals was suppressed by a passivation film of AlF₃, thecorrosion of the surface of the electromagnetic wave permeation windowwas prevented. It was also confirmed that no particle was formed in thepassivation film of AlF₃.

Since aluminum nitride constituting the electromagnetic wave permeationwindow 70 has high strength (>350 MPa) and high thermal shock resistance(Tc>400° C.), rise in the temperature following absorption of themicrowaves caused no damage.

AlN shown in Table 3 is one sintered by hot pressing with addition of Y₂O₃, and has high strength. Other AlNs were also tested. For example,with respect to an electromagnetic wave permeation window made of AlNwith no addition of Y₂ O₃ and having the properties of strength of 250MPa, heat conductivity of 50 W/mK, thermal shock resistance ΔTc =300°C., it was confirmed that neither damage nor melting occurred as in theabove case.

During the generation of plasma, the surface temperature of theelectromagnetic wave permeation window reached about 250° C.

If ΔTc>300° C., no practical problem occurs. The electromagnetic wavepermeation body made of aluminum nitride can be produced itself by asintering process, a chemical gas phase growing process, or a physicalgas phase growing process. When the temperature of the electromagneticwave permeation window is 250° C., the dielectric loss is sufficientlylow.

On the other hand, the electromagnetic wave permeation window 70 wasmade of quartz, and this electromagnetic wave permeation window 70 wasdamaged with the ECR plasma. Microscopically, the surface was meltedwith the ECR plasma. Further, the scanning type electron micrographrevealed that the surface of the electromagnetic wave permeation window2 was corroded, and that its surface got rough.

In Comparative Example 2, the electromagnetic wave permeation window 70was made of Al₂ O₃, which was broken due to rise in temperaturefollowing the adsorption of the microwaves.

Next, in the example above mentioned polysilicon was etched by usingClF₃, NF₃, Cl₂, SiH₂ Cl₂, or CF₃. The electromagnetic wave permeationwindows 2 were free from abnormality. In this way, it was clarified thatthe present invention is general-purpose for ECRs using varioushalogen-based corrosive gases.

Further, in above Examples and Comparative Example 1, polysilicon wasetched with use of Ar. As a result, neither damage nor permeation lossoccurred. Microscopically, the surface was melted with the ECR plasma.

Further, in the above Examples, polysilicon was etched by using O₂ orN₂. As a result, neither damage nor permeation loss occurred. That is,the surface was not melted with the ECR plasma. In this way, it wasclarified that the present invention exhibits durability against ECRsusing various inert gases or halogen-based corrosive gases.

In the embodiment shown in FIG. 14, the ECR etching apparatus of anon-bias type was shown. However, in order to apply AC bias, anelectrode can be provided inside the susceptor 74 to apply highfrequency electric power.

Further, according to the present invention, besides the electromagneticwave permeation body, a cover for an electrostatic capacity analyzer maybe made of aluminum nitride so as to measure the velocity of ions in theECR plasma. Further, a tube to be installed in a location for installinga helicon plasma antenna may be made of aluminum nitride.

The frequency range of the electromagnetic waves permeating theelectromagnetic wave permeation body according to the present inventionis not more than 300 GHz. Among the frequency range, the magnetic wavepermeation body according to the present invention finds itsparticularly useful application as microwave permeation bodies. Thefrequency range of the microwaves is 300 MHz to 300 GHz. However, sincethe properties of aluminum nitride in the range of 1 MHz differ fromthose at 10 GHz, the above effects can be exhibited even in thefrequency range of 1 MHz to 300 MHz. However, as the frequencyincreases, a material having a smaller dielectric loss tan δ ispreferred.

What is claimed is:
 1. A plasma generating electrode device,comprising:a joint-free monolithic substrate made of a dense ceramicsinter; and a planar plasma electrode comprising bulk metal embedded insaid substrate, said electrode being isolated from a setting face of thesubstrate and arranged to generate plasma above the substrate.
 2. Theplasma generating electrode device set forth in claim 1, wherein aresistance heating body made of a metal having a high melting point isembedded in the substrate, said plasma generating electrode device beingconstituted such a that surface of the substrate on a plasma-generatingside is heated by feeding electric power to the resistance heating body.3. The plasma generating electrode device set forth in claim 1, whereina volume resistivity of an electromagnetic wave permeation layerexisting between said electrode and that surface of the substrate on aplasma-generating side is not less than 10⁸ Ωcm, and a resistance ofsaid electrode is not more than 1Ω.
 4. The plasma generating electrodedevice set forth in claim 1, wherein a wafer is attracted onto saidsetting face by generating an electrostatic capacity by applying a DCvoltage to said electrode, and plasma is generated by feeding highfrequency signals to said electrodes via an insulating transformer. 5.The plasma generating electrode device set forth in claim 1, wherein theaverage thickness of the electromagnetic wave permeation layer is atleast 0.1 mm.
 6. The plasma generating electrode device set forth inclaim 5, wherein the average thickness of the electromagnetic wavepermeation layer is at least 0.5 mm.
 7. The plasma generating electrodedevice set forth in claim 5, wherein the average thickness of theelectromagnetic wave permeation layer is at least 5 mm.
 8. The plasmagenerating electrode device set forth in claim 1, wherein said electrodehas a plate-shaped body having a plurality of small holes.
 9. The plasmagenerating electrode device set forth in claim 8, wherein said electrodeis a mesh electrode, the width of wires of said mesh electrode is notmore than 0.8 mm, and the number of crossing wires per one inch is notless than
 8. 10. The plasma generating electrode device set forth inclaim 1, wherein the thickness of said electrode is not less than 20 μm.11. The plasma generating electrode device set forth in claim 5, incombination with a semiconductor production unit using a halogen-basedcorrosive gas, said plasma generating electrode device being adapted tobe used to generate plasma of said halogen-based corrosive gas byapplying high frequency voltage upon the halogen-based corrosive gas.12. The plasma generating electrode device set forth in claim 5, whereinsaid substrate is made of a nitride-based ceramic.
 13. The plasmagenerating electrode device set forth in claim 12, wherein at least saidelectromagnetic wave permeation layer of the substrate is made ofaluminum nitride, said aluminum nitride having a dielectric loss tan δof not more than 10⁻¹, and a thermal shock resistance ΔTc of not lessthan 250° C.
 14. The plasma generating electrode device set forth inclaim 12, wherein the content of impurities in said aluminum nitride isnot more than 1%, and a relative density thereof is not less than 99%.15. An electrode-embedded article comprising a joint-free monolithicsubstrate made of a dense ceramic sinter, and a plasma-generatingelectrode embedded in said substrate and made of a planar metal bulk,said substrate surrounding said electrode being free from a joint face.16. The electrode-embedded article set forth in claim 15, in combinationwith a semiconductor production unit using a halogen-based corrosivegas.
 17. The electrode-embedded article set forth in claim 15, incombination with a semiconductor production unit, and wherein saidelectrode comprises a metal having a high melting point, said metalbeing selected from the group consisting of tantalum, tungsten,molybdenum, platinum and alloys thereof.
 18. The electrode-embeddedarticle set forth in claim 15, wherein said electrode is a planarelectrode made of a plane body having a plurality of small holes. 19.The electrode-embedded article set forth in claim 18, wherein saidelectrode is a mesh electrode.
 20. A process for producing anelectrode-embedded article, comprising the step of hot press sintering aceramic molding and a plasma-generating electrode made of a planar metalbulk under pressure applied in a thickness direction of said electrode,thereby embedding said electrode in a dense substrate made of amonolithic sinter free from a joint face.
 21. The process for producingthe electrode-embedded article set forth in claim 20, wherein saidceramic molding in which said electrode is embedded is obtained by thesteps of producing a preliminary molding, placing said electrode on saidpreliminary molding, applying a ceramic powder on said preliminarymolding and said electrode, and uniaxially molding the resultant. 22.The process for producing the electrode-embedded article set forth inclaim 20, wherein two moldings having a relative density of 60% areproduced, said electrode is sandwiched between said two planar moldings,and said two planar moldings and said electrode are hot pressed in thisstate.
 23. The process for producing the electrode-embedded article setforth in claim 22, wherein powdery aluminum nitride having the contentof not more than 1% of metallic impurities is used as said ceramicpowder, and said substrate having a relative density of not less than99% is obtained.
 24. An electromagnetic wave permeation body for use ina plasma-generating device for generating plasma to a gas, comprising: asusceptor comprising a joint-free monolithic substrate made of a denseceramic sinter; anda planar plasma electrode comprising bulk metalembedded in said substrate, wherein at least that surface of saidelectromagnetic wave permeation body which is to contact an atmospherein which plasma is generated comprises aluminum nitride, said aluminumnitride having a dielectric loss, tan δ, of not more than 10⁻² and athermal shock resistance ΔT of not less than 300° C.
 25. Theelectromagnetic wave permeation body set forth in claim 24, whereinplasma of a halogen-based corrosive gas is generated upon application ofthe high frequency electric power upon said gas.
 26. The electromagneticwave permeation body set forth in claim 25, wherein said halogen-basedcorrosive gas is at least one kind of a halogen-based corrosive gasselected from the group consisting of CF₄, ClF₃, NF₃, Cl₂, SiH₂ Cl₂ andCF₃.
 27. The electromagnetic wave permeation body set forth in claim 25,wherein a passivation film made of aluminum fluoride is formed on asurface of said electromagnetic wave permeation body.
 28. A plasmagenerating electrode device, comprising:a joint-free monolithicsubstrate made of a dense ceramic sinter; a resistance heating bodyembedded in said substrate; and a planar plasma-generating electrodecomprising bulk metal embedded in said substrate between said resistanceheating body and a setting face of said substrate, said electrode beingisolated from the setting face of the substrate and arranged to generateplasma above the substrate.